How do we measure the mass of an extrasolar planet?
A) We use Newton's law of gravity, using the measured distance of the planet from its star and the planet's gravitational pull on the star.
B) We measure the change in the brightness of a distant star that the planet causes by microlensing.
C) We use spectra to measure the planet's temperature and photometry to measure its brightness.
D) We measure the planet's angular diameter and hence its size and then use spectra to find its composition and hence density.

Question

Quizplus · Accepted Answer

We use Newton's law of gravity, using the measured distance of the planet from its star and the planet's gravitational pull on the star, to determine the mass of an extrasolar planet. This is done by observing the planet's effect on the motion of its host star, such as the wobble in the star's position or changes in the star's velocity.

How Do We Measure the Mass of an Extrasolar Planet